A single phase permanent magnet motor usually consists of a stator core, stator windings, and a permanent magnet rotor. The stator core is generally U-shaped, including two spaced pole arms. A pole claw is formed at a distal end of each pole arm. An inner wall surface of each pole claw is inwardly recessed to form an arc pole surface. The windings are wound around the pole arms. The rotor is disposed between the two pole claws and confronts the arc pole surface with a generally even air gap formed there between.
For facilitating startup of the rotor, the arc pole surface is inwardly recessed to form a startup groove. The startup groove is offset from a central axis of the pole claw, such that when the rotor stops rotation after motor is powered off, a pole axis of the rotor is offset from the central axis of the pole claw by an angle to form a startup angle. Under the driving of a corresponding startup circuit, the rotor can be successfully started along a specific direction when the motor is energized. However, the above single phase permanent magnet is incapable of bidirectional startup, which limits its application.